President Barack Obama addresses the 68th session of the United Nations General Assembly on Tuesday. (Richard Drew / AP)

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Flashpoint: Syria----- U.N. chemical weapons inspectors returning to SyriaGENEVA — The United Nations says the team of chemical weapons inspectors led by Swedish expert Ake Sellstrom will return to Syria on Wednesday. U.N. officials in Geneva say Sellstrom's team will return to complete its investigation into "pending credible allegations" of chemical weapons use in the civil-war struck Arab state. In the statement Tuesday, the U.N. said the investigation will include gathering evidence from an alleged chemical weapons attack on March 19 on the village of Khan al Assal outside the city of Aleppo, which was captured by the rebels in July. On its previous trip to the country, the team compiled a report that said nerve agent sarin was used in an Aug. 21 attack near Damascus. — AP

UNITED NATIONS — President Barack Obama said Tuesday the U.N. Security Council must agree to a resolution on Syrian chemical weapons that includes consequences for President Bashar Assad if he doesn't meet demands to dismantle his stockpile.

Obama challenged the U.N. to include such accountability in any resolution, saying the international body's reputation is at stake.

"If we cannot agree even on this," he said, "then it will show that the United Nations is incapable of enforcing the most basic of international laws."

The United States and Russia have brokered an agreement for Syria to give up its chemical weapons. But the countries are at odds on what the possible consequences would be if Syria doesn't comply.

"We believe that as a starting point the international community must enforce the ban in international weapons," he said in his address to the U.N. General Assembly.

The agreement between Washington and Moscow came as Obama was pushing Congress to approve a military strike against Syria for a chemical weapons attack last month on civilians outside Damascus that the Obama administration says was carried out by Assad's regime. The subsequent diplomatic steps agreed to by U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov placed the threat of force on hold.

Still, The Russians have challenged the administration's claims of Assad culpability and Assad has blamed rebel forces for the attack.

Obama aggressively pushed back against those claims in his speech Tuesday.

"It's an insult to human reason and to the legitimacy of this institution to suggest that anyone other than the regime carried out this attack," the president said.

Obama also said that while the international community has recognized the stakes involved in the more than 2-year-old civil war, "our response has not matched the scale of the challenge."

Obama announced that the United States will provide $339 million in additional humanitarian aid to refugees and countries affected by the Syrian civil war, bringing the total American aid devoted to that crisis to nearly $1.4 billion. The White House said the aid will include $161 million spent inside Syria for medical care, shelter and sanitation projects, with the remainder going to help Syrian refugees in Lebanon, Jordan, Iraq, Turkey and Egypt.

Obama reiterated his demand that Assad cannot continue to lead Syria, but said he would not use U.S. military force to depose him.

"That is for the Syrian people to decide," he said. "Nevertheless, a leader who slaughtered his citizens and gassed children to death cannot regain the legitimacy to lead a badly fractured country."

He called on Assad allies to stop supporting his regime.

"The notion that Syria can somehow return to a pre-war status quo is a fantasy," he said. "It's time for Russia and Iran to realize that insisting on Assad's role will lead directly to the outcome that they fear: an increasingly violent space for extremists to operate."